Datasheet LT4363 (Analog Devices) - 17
| Hersteller | Analog Devices |
| Beschreibung | High Voltage Surge Stopper with Current Limit |
| Seiten / Seite | 24 / 17 — applicaTions inForMaTion. Design Example |
| Dateiformat / Größe | PDF / 255 Kb |
| Dokumentensprache | Englisch |
applicaTions inForMaTion. Design Example
Modelllinie für dieses Datenblatt
- LT4363CDE-1#PBF LT4363CDE-1#TRPBF LT4363CDE-2#PBF LT4363CDE-2#TRPBF LT4363CMS-1#PBF LT4363CMS-1#TRPBF LT4363CMS-2#PBF LT4363CMS-2#TRPBF LT4363CS-1#PBF LT4363CS-1#TRPBF LT4363CS-2#PBF LT4363CS-2#TRPBF LT4363HDE-1#PBF LT4363HDE-1#TRPBF LT4363HDE-2#PBF LT4363HDE-2#TRPBF LT4363HMS-1#PBF LT4363HMS-1#TRPBF LT4363HMS-2#PBF LT4363HMS-2#TRPBF LT4363HS-1#PBF LT4363HS-1#TRPBF LT4363HS-2#PBF LT4363HS-2#TRPBF LT4363IDE-1#PBF LT4363IDE-1#TRPBF LT4363IDE-2#PBF LT4363IDE-2#TRPBF LT4363IMS-1#PBF LT4363IMS-1#TRPBF LT4363IMS-2#PBF LT4363IMS-2#TRPBF LT4363IS-1#PBF LT4363IS-1#TRPBF LT4363IS-2#PBF LT4363IS-2#TRPBF LT4363MPMS-1#PBF LT4363MPMS-1#TRPBF LT4363MPMS-2#PBF LT4363MPMS-2#TRPBF LT4363MPS-1#PBF LT4363MPS-1#TRPBF LT4363MPS-2#PBF LT4363MPS-2#TRPBF
Textversion des Dokuments
LT4363
applicaTions inForMaTion
significantly by locating resistive dividers close to the pins Choose 4.99kΩ for R2. with short VCC and GND traces. (27V–1.275V)•R2 R1= =100.7kΩ
Design Example
1.275V As a design example, take an application with the follow- The nearest standard value for R1 is 100kΩ. ing specifications: VCC = 8V to 14V DC with a transient of 150V and decay time constant (τ) of 400ms, V Next calculate the sense resistor, RSNS, value: OUT ≤ 27V, current limit (ILIM) at 5A, low battery detection of 6V, input 50mV 50mV overvoltage level at 60V, and 1ms of overvoltage early RSNS = = =10mΩ ILIM 5A warning (Figure 8). Selection of SMAJ58A for D1 will limit the voltage at the CTMR is then chosen for 1ms of early warning time: VCC pin to less than 71V during 150V surge. The minimum 1ms•6µA required voltage at the V C = 60nF CC pin is 4V when VIN is at 8V; TMR = 100mV the supply current for LT4363 is 1.5mA. The maximum value for R7 to ensure proper operation is: The nearest standard value for CTMR is 47nF. 8V – 4V Finally, calculate R4, R5, and R6 for 6V low battery detec- R7 = = 2.67kΩ 1.5mA tion and 60V input overvoltage level: Select 1kΩ for R7 to accommodate all conditions. R5+R6 6V • =1.275V R4+R5+R6 The maximum current through R7 into D1 is then calcu- lated as: R6 60V • =1.275V 150V – 64V R4+R5+R6 I = 86mA D1= 1kΩ Choose 10kΩ for R6. which is easily handled by the SMAJ58A for more than 60V •10kΩ 500ms. R4+R5= –10kΩ = 460.6kΩ 1.275V With 0.1µF of bypass capacitance, C2, along with 1k of 460.6kΩ+10kΩ R7, high voltage transients up to 200V with a pulse width R5=1.275V • –10kΩ = 90kΩ less than 10µs are filtered out at the V 6V CC pin. Next, calculate the resistive divider value to limit VOUT to R4 = 460.6kΩ – 90kΩ = 370.6kΩ 27V during an overvoltage event: Select 90.9kΩ for R5 and 374kΩ for R4. 1.275V • R ( 1+R2) V = 27V The pass transistor, Q1, should be chosen to withstand a REG = R2 short-circuit with VCC = 14V. In the case of a severe output Set the current through R1 and R2 during the overvoltage short where VOUT = 0V, the total overcurrent fault time is: condition to 250µA. 47nF •0.875V tOC = = 0.904ms 1.275V 45.5µA R2= = 5kΩ 250µA 4363fb For more information www.linear.com/LT4363 17 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Typical Application Related Parts
applicaTions inForMaTion
significantly by locating resistive dividers close to the pins Choose 4.99kΩ for R2. with short VCC and GND traces. (27V–1.275V)•R2 R1= =100.7kΩ
Design Example
1.275V As a design example, take an application with the follow- The nearest standard value for R1 is 100kΩ. ing specifications: VCC = 8V to 14V DC with a transient of 150V and decay time constant (τ) of 400ms, V Next calculate the sense resistor, RSNS, value: OUT ≤ 27V, current limit (ILIM) at 5A, low battery detection of 6V, input 50mV 50mV overvoltage level at 60V, and 1ms of overvoltage early RSNS = = =10mΩ ILIM 5A warning (Figure 8). Selection of SMAJ58A for D1 will limit the voltage at the CTMR is then chosen for 1ms of early warning time: VCC pin to less than 71V during 150V surge. The minimum 1ms•6µA required voltage at the V C = 60nF CC pin is 4V when VIN is at 8V; TMR = 100mV the supply current for LT4363 is 1.5mA. The maximum value for R7 to ensure proper operation is: The nearest standard value for CTMR is 47nF. 8V – 4V Finally, calculate R4, R5, and R6 for 6V low battery detec- R7 = = 2.67kΩ 1.5mA tion and 60V input overvoltage level: Select 1kΩ for R7 to accommodate all conditions. R5+R6 6V • =1.275V R4+R5+R6 The maximum current through R7 into D1 is then calcu- lated as: R6 60V • =1.275V 150V – 64V R4+R5+R6 I = 86mA D1= 1kΩ Choose 10kΩ for R6. which is easily handled by the SMAJ58A for more than 60V •10kΩ 500ms. R4+R5= –10kΩ = 460.6kΩ 1.275V With 0.1µF of bypass capacitance, C2, along with 1k of 460.6kΩ+10kΩ R7, high voltage transients up to 200V with a pulse width R5=1.275V • –10kΩ = 90kΩ less than 10µs are filtered out at the V 6V CC pin. Next, calculate the resistive divider value to limit VOUT to R4 = 460.6kΩ – 90kΩ = 370.6kΩ 27V during an overvoltage event: Select 90.9kΩ for R5 and 374kΩ for R4. 1.275V • R ( 1+R2) V = 27V The pass transistor, Q1, should be chosen to withstand a REG = R2 short-circuit with VCC = 14V. In the case of a severe output Set the current through R1 and R2 during the overvoltage short where VOUT = 0V, the total overcurrent fault time is: condition to 250µA. 47nF •0.875V tOC = = 0.904ms 1.275V 45.5µA R2= = 5kΩ 250µA 4363fb For more information www.linear.com/LT4363 17 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Typical Application Related Parts